C language operators and input and output

1. Operator
2. An operator
3. Input and output
4. Control statement

1、 Operator

Single calculation, moving customs and , Exclusive or logic

Monocular operator 、 Arithmetic operator 、 Move left, move right 、 Relational operator 、 Bitwise AND , Exclusive or 、 Press bit or 、 Logical operators 、 Conditional operator 、 assignment

1.1 Arithmetic operator

+、-、*、/、%、++、--

Be careful ：% Can't be used with floating point numbers

++ before ：++a Add it first , To assign a value

++ After ：a++ Assign first , Self adding

1.2 Relational operator

>、<、>=、<=、==、!=

Be careful ：0 < a < 5 //error

Equal sign writing ：

1.3 Logical operators

&& 、|| 、 ！

expression 1 && expression 2

&& The law of truncation ： One is false , The result is false , If the previous one is false , There will be no operation later

expression 1 || expression 2

|| The law of truncation ： One is true , That's true , The previous one is true , There will be no more operations later

Case study 2：

1.4 sizeof Operator

sizeof( data type )  or  sizeof( Variable name )

1.5 Ternary operator

expression 1？ expression 2： expression 3

Judging expressions 1 Is the value of true , If set up , Expression 2 As the value of the entire expression , otherwise , Expression 3 As the value of the entire expression

1.6、 The comma operator

expression 1, expression 2, expression 3 …… expression n

Execute each expression from left to right , Expression n As the value of the entire expression

Be careful ： The comma operator has the lowest priority , Use parentheses

Case study 1：

1. set up int i=2,j=3,k=4,a=4,b=5,c=3;, Then execute the expression （a=i<j）&&(b=j>k)&&(c=i,j,k) after ,c The value is （3）

2、 An operator

&、|、~、^、<<、>>

2.1 And operation （&）

1101 0011

& 0110 1110

  0100 0010

Case study ： take 1101 0011 Of 0~2 A reset

  1101 0011

& 1111 1000 （~0000 0111）

  1101 0000

2.2 Or operations

 1010 0101

| 1110 1011

 1110 1111

Case study ： take 1010 0101 Of 3~5 A into 101

1010 0101

& 1100 0111

  1000 0101

|  0010 1000

   1010 1101

2.3 Take the opposite

~1010 1111 --->0101 0000

2.4 Exclusive or

Same as 0, Different for 1

  1101 0010

^ 1000 1001

  0101 1011

2.5 Move left

Move left ： High level discard , Low complement 0

2.6 Move right

An unsigned number ： To discard in low order , High compensation 0

Signed number ： To discard in low order , High compensation 1

3、 Input and output

function ： Modules with independent functions

Standard I / O functions ：scanf、printf（ There are no restrictions on variable types ）

Input and output of characters getchar、putchar

Input ： Copy data from keyboard to memory

Output ： Copy data from memory to the display

3.1 Output

int printf(“ Format control string ”, Output table );

Format control string ： Output as is （ It saves ） + Formatter

Output table ： Object to output

integer ：

%d： Decimal integer

%o： Octal integer

%x、%X： Hexadecimal integer

#： Automatically prefix octal and hexadecimal

%u： An unsigned integer

%hd：short type

%ld：long type

%lld：long long type

character ：

%c： Character

floating-point ：

%f：float

%lf：double

%e： Index

%g： Choose the shorter of decimal and exponential

.n： Retain n Decimals

m： Specify the domain width of our output , The default is right alignment ,m The value of is greater than the actual length of the data , Fill in the space on the left , otherwise

, Original output

3.2 Input

int scanf(“ Format control string ”, Address table );

Be careful ：

1. scanf In the format string statement , Don't add modifiers , If you want to add , Input as is
2. If input “%d%d” Assign values to multiple variables , There is no interval in the format string , Then when typing on the keyboard , With spaces 、 enter 、Tab The key ends as the input of a variable
3. All input ends , Must end with carriage return
4. If it is “%c%c“ when , There should be no blank space when inputting 、 enter 、Tab key , Because of the space 、Tab key 、 Carriage return is also a character

terms of settlement ：1、%c%c Add a space or comma between （ Input as is ）

          2、 Add %*c,* Represents the time suppressor

3.3 Input and output of characters

int getchar();

Return value ： Characters obtained from the keyboard ASCII code

char a;

a = getchar（）;

int putchar（int c）;

Parameters c： What you want to output ASCII Code value